Refrigerator defrosting control



Jan. 19, 1954 M. s. SUTTON 2,666,299

REFRIGERATOR DEFROSTING CONTROL 6 Filed April 8, 1950 L2 K l 5aINVENTOR. MYER SUTTON WMCM'KL ATTORNEYS Patented Jan. 19, 1954 J Y :11?1 Lv f:

EEEQIGEEMAQRDEFROSTINQGQMEQE' v M Sutton Bfinneapolis; Min-m, assignorto 1110- It"; S. Thermo Control. 00., Minneapolis,MinngatcorporaitimofiVI-innesotm 1? To fr s h d f us r ite li tomaxr toe m dim i i rans er h uree. ne v e u' rw "n i awe-me m et-the aoeumolated frost laye the'prior art re} t3 1w e r tin i wmarr o; 2 9 any"oneoifseyer Stash, a'h'ot gas from th cIo'secf' refrigerating system,irk'stanees electrieai 5e" w h v through aresietahee'heatr'tha"is: eonta*with or atijj' ent the''ol'cf; dififu fil ieatiofie, howe'v 7 th'throngh'a cement 061115110 tfie 'flowof the" media" v tibr'i bf the" How'ezshtrer devic by a" system whici'r genera y device "which is'cafiafiie a eontroi'devioefora'preetermi after "which the How oritrolj'device is n'ra operative to terminate theiefroting opei tijqn.

'1 The handicap of thisjririof art arrahgernent has been that the laye'r6f frost aeoum'ulated on the e'oid' diffuser viziild r ar y fdpthtiepending on th moistuie content Ethe oo-mifig into dontat the eolddrfiuser whi r gmresul't from rariat iom the m oisttxrecontent q maria-1s maintaindw hin'a storage space wh ihathe cold diffu I is situated. thetiming 'meohanisms: useithe: prior} art were not efiectiveto adjustdefto'sting yer-fed in acnortfance with the variation 01 the thicknessof the frost layer.

timing, heretofore mvrdmwe of adiustableiicharaeter; leach adiutmentdeej intrequently thepperator would notheable-to gage the eertii'oriorart ii aude t is mz' timer was either inadequee to ,prqriqe torWhile it is trueflthatmost I This latter condition: is t the mlq feteiemere i of mrt; 01" eirseth f ir in iod; wesirermiiirdi to xtmdif-QI pi d of: wh ch; wa great r than ,was. 8-9: tuallyneoessarytq completely;remove; the; frost. n w i h mu txtr mely-harem, be fi i r y' when: he 9mdifiuser is used in conjunction-with, a st age space in whichperighabl'e products-snob a gse= cause if the celeb qifiu er i rie teqa-fter the mitt hae been removed and evenfor; a moderate l e gth ofitime;it will heat thestorage spape-to the ex= tent of thawihg-- or-e verrpartial-h thawing the perishable prodirets -wh ighwil depreciate thenatnral fiavor and the keeping-qualities of. such products even though;the temperature may still be;- in the; range-immediately below thefreezin temperature: of water: ge ene tests have established thatseverely frozen; foods whieh are normaltrsmaintained at temperatures of;0 or l'owerare damagect in their taste, keeping qnali ties: and:possibly -i n---.their vitamin eontent if during "storage thetemperature of *;thap1;od uets Rut-permitted: to rise tos -asmueh as zfifip the important feature in regulating the defrosti-ng of: colddiffusersaby. the-nee or a treating medium is; tcrterminate the flowheating metfi um to'ethedifiusezsimmediately after frosthas heenremovectso that the diffuserwill not raqiate heairto misethe temperature ofthe'surroundfing space;r i v invention disclosed inathis application isa modifieatiom ofi the disclosure shown in the co- Dfit g}.apnlication-otFreder-iek M;Jones,-Ser; No. 158,053, nows-xUnitem'states Patent No. $509,939,- gmmed Mayrfifi, 19.551, .whichds assigneqtothe present assignea. i

the resent. disclosure amore or 1%s- -eon'- ventional timing devicethrough the medium oi a monlertarilr.elosee:switch,,1mttates theop a-21. f 2 32W fiOiltrolgdevicei also sets up a ho ng: oircuit, maintainsthe-flow onerativet-conditionltoflbring A- normally.=closed switch v ving the defrosting operation substantially-immee diately after theremoval of the accumulated frost and without regard to the length oftime required for the defrosting operation to occur.

Another object is to provide a simple electrical control system forsupervising the operation of a defrosting control device, whichregulates the flow of an energy transferring medium to a cold diffuser,in which the control device is made operative by the momentary closureof a normally open switch, and is terminated by the opening of anormally closed switch whose action is responsive to the temperature ofthe diffuser.

A further object is to provide a control system for a defrosting controldevice which includes a control circuit that is energized by a firstswitch in the circuit which establishes a holding circuit that is brokenby the opening of a normally closed switch in the circuit which isresponsive to a rise of temperature adjacent the cold diffuser when thefrost accumulation has been removed from the latter by the applicationof heat.

Other and further objects may become ap parent from the followingdescription and claims, and in the appended drawings in which:

Fig. 1 is a schematic showing of one form of refrigeration system withwhich the present invention is adapted for use in controlling thedefrosting of a cold diffuser; and,

Fig. 2 is a schematic diagram of a control system forming the presentinvention.

Referring now to the drawings and particularly to Fig. 1, is shown oneform of refrigeration system to which the present, invention applies.Reference numeral I indicates a conventional compressor which is drivenby a prime mover I2. The prime mover i2 may be either an electric motoror an internal combustion engine, and its operation is independent ofother portions of the system. While not shown, the prime mover 12 willgenerally be operated by control means which respond to a conditionwithin an enclosed space whose temperature is to be con trolled and,therefore, the prime mover will operate intermittently to maintain asubstantially constant condition.

Extending from the high pressure side or compressor I0 is a conduit [4which is joined to the upper end of a condenser !6. At its lower endcondenser I6 is joined by a conduit l8 which extends to one side of arefrigerant receiver 20. Extending from the other side of receiver 26 isa conduit 22 which is joined to the lower end of an evaporator 24.Mounted in conduit 22 is a conventional expansion valve 25 whoseoperation is controlled by a thermostatic bulb 28. Extending from theupper end of evaporator 24 is a conduit 38 which at its other end isjoined to a manifold 32 on the low pressure side of compressor I0.

Extending from a. T 34 in conduit i4 is a conduit 36 which at its otherend is joined to a T 88 connected in the evaporator 24. Mounted inconduit 36 is a flow control device or valve 48 whose operation iscontrolled by a motorizing mechanism 42, hereinafter disclosed as asolenoid operator.

A control box indicated at 44 contains the necessary mechanism foroperating the motorizmg portion 42 of valve 40 through a pair ofconductors 46. 48. A thermostatic bulb 58, having a connected tube whichextends to the control box 44, is supported on fins 52 which are securedto the outer surface of the evaporator 24 so that in effect bulb 50 isin thermal contact wit ap orator 24. Q

Referring now to Fig. 2 is schematically shown the control circuit, themajor portion of which is normally contained within the control box 44.shown in Fig. 1, together with valve 48 and its motorizing portion 42. Atiming device indicated at 54 has connected thereto a rotating switchmember 56 which is adapted on rotation to engage a stationary contactmember 58. The parts just described may take any one of a number offorms wherein after the passage of a predetermined period of time themovable switch 56 is suitably brought into engagement with the fixedcontact 58. and it should be understood that the movable switch 56 maybe adjustably positioned with respect to the timing mechanism 54 so asto engage the fixed contact 58 at regular predetermined intervals andthere may, if necessary, be one or more of the movable members 56 whichwill engage thefixed contact 58 at predetermined intervals even thoughthese intervals be less than twelve or twenty-four hours in which thenormal clock mechanism will make a complete rotation. As here shown, thetiming device is actuated by a motor 68.

Reference characters L1 and L2 are lineconductors extending from aconventional source of power, not shown. A conductor 62 extends fromconductor L2 to the moving switch contact 56. A conductor 64 extendsfrom conductor L2 to one side of motor 60 and conductor 66 extends fromthe other side of motor 60 to conductor L1 to provide for the operationof the electric motor 60.

A conductor 68 extends from the fixed contact 58 through a junction 10to a contact 12. A conductor 14 extends from a contact 16 to the lineconductor L2. A conductor 18 extends from junction 10 to a movableswitch blade which supports a contact 82 that is adapted to normallyengage a fixed contact v84. A conductor 85 extends from stationarycontact 84 through an induction coil 88 of a relay indicated at 90. Fromthe other end of the induction coil 88 a conductor 92 extends to theline conductor L1. Relay es carries an armature controlled switch 94which when the induction coil 88 is energized engages the contacts 12,16. Extending from a junction 96 on conductor 86 is a conductor 45 whichconnects to an induction coil I00 heretofore designated as themotorizing portion 42 of the valve 40, shown in Fig. 1. A conductor 48extends from the other side of the induction coil let to the lineconductor L1.

The movable switch 80 is connected to a bracket I04. On one side of theswitch 80 is a coil spring I06 which is adapted to resiliently holdcontact 82 in engagement with contact 84. A bellows I08 is mounted onthe other side of switch 80 and is connected through tube 5! to thethermostatic bulb 50, being the same which is shown in Fig. 1. Whileswitch 86 is here shown as being actuated by an independent fluidthermostat, the switch may be composed of a bimetallic element containedwithin a cartridgelike casing.

The operation of the refrigeration system shown in Fig. 1 isconventional but for a further understanding, the evaporator 24, whichmay be regarded as a cold difiuser, would normally be situated within anenclosed space whose temperature is to be controlled. The prime mover 12will, through control means not shown, be responsive to the conditionwithin the enclosed space in which the cold diffuser is mounted and suchcontrol means will periodically call for the capacity. which liquid isti ereducedpress retina sen. .Th ,,.vap zed frefrrg rat an, 1 throughthe 'c'dn'duit 30 t6 the header 32 the low pressure sideof thecompressor. on entering the compressor the vapors are compressed eieWainw htc een;Meaga denser T6 from whence the condenser vapors willreturn to the receiver 20'.

Tdeffect defrosting of the.evaporatorxbrucold diffuser 24,valveAiLisiopehed its motorizing mechanism 42 .to permithotga'sesfromthe pres ure side .of the refrigerant systemhto fiow nor-n.1, 34 through.therconduit v36 arid-T038 into evaporator, In practice, the prime mover.l 2 iivill. be operating duringthe defrostingwperation becausethewevaporator WiILvery likely-be coated with a suflicient layer offrost so as to insulate the diffuser from the enclosed space to such anextent that the refrigerating needs of the enclosed space will requireoperation of the prime mover.

Referring now to Fig. 2, the moving contact 56 will be adjustablymounted with respect tothe timing device 54 so as to bring about adefrosting operation after a predetermined period of time from the lastdefrosting operation. Assuming now that the movable switch 56 hasengaged contact 58, a circuit will be established which may be traced asfollows. From the conductor L2 through conductor 62, switch 56, contact58, conductor 68 to junction 10, thence through conductor 18 to switch80, and thence through the closed contacts 82, 84 and the conductor 86to the junction 96, thence through the induction coil 88 and conductor92 to the line conductor L1. Current will also flow from junction 96through the conductor 46 and induction coil I into conductor 48 to theline conductor L1. This will complete a circuit to cause simultaneousclosing of the relay 90 and opening of the motorizing portion 42 of thevalve 40. When relay 99 is energized, the armature connected switch 94engages the contacts 76, 12 to establish a holding circuit which may betraced as follows. From the line conductor L2 through conductor ?4 tocontact 16, thence through switch 94 to the contact 12, and thencethrough conductor 68 to junction 10. From junction 19 current will flowthrough the conductor 18, switch 80, contacts 82, 84, conductor 86 toand through the induction coils 88 and I90 and thence to the lineconductor L1 through conductors 92 and 48. The last named circuit is aholding circuit because the movable switch 56 will only make a momentarybrushing engagement with the stationary contact 58 and as the timingdevice 54 continues its operation the circuit will be broken through theswitch 56, 58 so that the holding circuit through relay 90 maintains themotorizing device 42 of valve 40 in operative condition. While thediffuser 24 is coated with frost, the thermostatic illin. will refletarqld con iti niana th lf ill deflate .hprersrrwh -t e f s I di userflabrmeitme.t amt t iv res q d ari in temii atufe Qftl fi tfiiscir w ich i"toc a ion y ne as tha is n er n the f e h e T1 8 I i 's"i ..te ii er mrof the di u r j "systeiji within the thermostat to; .Tefi en r nsiemctherbefiows its a aint rri lttic. reth -pswitenh ade MupWardly {to breakengagement between the normall closed ,I'IIHQSQ, :ccn acts. ar th quethe ind ct n ck aandthisi eq .;b .e..tc.- ha 1min circuit establi hed scan n-.55... thr u h .hpldine i; when, inciu e g ie relay 9.0.1TYII1S,at er. sti wciimno manr o cur by re on dfeugagemmfi.Qfmntacts..56., 5.8,.ther'e. is mile" r rimmed; r mancin thev th rm static d vi e.W li igidit esrcndto ar segiritmperatir medimi r in br ak the def tingcirti ti a heavy coating p rost has been e tab ished. on tIie-dtuser.ihe ermostatic I str c win i t r'e's'nq ic t scheme of conditionsa d: all Of the frost has. been removed mm the rfa egf'tiieplifiusr, .4t 1? t ss lqft f rese l ti fi reside Y 1. Siii circuit for-continuingthe .qbfi jfid lfifia new; cen 1....c vi e wherema field? op switch ismomenta iiy closed and wherein the holding circuit which operates thecontrol device is broken by a normally closed thermostatic switch whichis also in the circuit. By this simple arrangement variations in thethickness of the layer of frost on the diffuser will have no effect andneed not be compensated for by adjustment of the timing means. Thecircuit will always be broken as soon as a slight rise in temperatureoccurs at the diffuser, which will follow removal of the frosted layer.Under these circumstances the diffuser will not radiate damaging heatinto the enclosed space since the normal refrigerant fluid circuit willagain be established as soon as the flow control device is closed andthe diffuser will again be rapidly cooled by evaporation of refrigerantfluid.

My invention is defined in the terms of the appended claims.

I claim:

1. A system for controlling the operation of a defrosting controldevice, comprising a first circuit including a motor operativelyconnected to the control device and which when energized activates thecontrol device to initiate defrosting of a cold diffuser, a source ofpower, a normally closed switch in the circuit between the source ofpower and the motor, a normally open switch in the circuit between thesource of power and said first named switch, said second named switchwhich when closed being effective to energize said motor, a relaysolenoid in said circuit which is energized simultaneously with themotor and concurrently closes a pair of relay contacts, and a secondcircuit including the source of power, said relay contacts, said firstnamed switch, the relay solenoid and said motor, said second circuitbeing effective to maintain'energization of the motor independent of thesecond named switch, said first named switch on opening being effectiveto de-energize either of said circuits.

2. A system for controlling the operation of a defrosting controldevice, comprising a first circuit including a motor operativelyconnected to the control device and which when energized activates thecontrol device to initiate defrosting of a cold diffuser, a source ofpower, a normally closed switch in the circuit'between the source ofpower and the motor, a normally open switch in the circuit between thesource of power and the first named switch, said second named switchwhich when closed being effective to energize said motor, a relaysolenoid in said circuit which is energized simultaneously with themotor and concurrently closes a pair of relay contacts, a second circuitincluding the source of power, contacts of said relay, said first namedswitch, said relay solenoid and said motor, said second circuit beingeffective to maintain energization of the motor independent of thesecond named switch, and temperature responsive means operativelyconnected to said first named switch being efiective to open said switchand tie-energize either of said. circuits to terminate operation of thecontrol device.

3. A system for controlling the operation of a defrosting controldevice, comprising a first circuit including a motor operativelyconnected to the control device and which when energized activates thecontrol device to initiate defrosting of a cold difiuser, a source ofpower, a normally closed switch in the circuit between the source ofpower and the motor, a normally open switch in the circuit between thesource of power and said first named switch, said second named switchwhich when closed being effective to energize said 8 motor, timing meansoperativel'y associated with said second named switch being efiective tomoinentarily close the second named switch and thereafter move the sameto an open position, a relay solenoid in said circuit which is energizedsimultaneously with the motor and concurrently closes a pair of relaycontacts, a second circuit including the source of power, said relaycontacts, said first named switch, the relay solenoid and said motor,said second circuit being effective to maintain energization of themotor after the timing means has again opened the second named switch,and temperature responsive means operatively connected to said firstnamed switch being effective to open said switch to ole-energize eitherof said circuits in response to a change of temperature.

MYER S. SUTTON.

References Cited in the file or this patent UNITED STATES PATENTS,

Number Name Date 1,913,433 Doble, Jr. June 13, 1933 2,081,479 Fink May25, 1937 2,313,390 Newton Mar. 9, 1943 2,333,432 Lum Nov. 2, 19432,451,682 Lund- Oct. 19, 1948 2,525,560 Pabst Oct. 10, 1950 2,551,163Rickert et a1 May 1, 1951

